Ir and/or Sm promoted multi-metal oxide catalyst

ABSTRACT

A catalyst comprising a promoted mixed metal oxide is useful for the vapor phase oxidation of an alkane or a mixture of an alkane and an alkene to an unsaturated carboxylic acid and for the vapor phase ammoxidation of an alkane or a mixture of an alkane and an alkene to an unsaturated nitrile.

[0001] The present invention relates to an improved catalyst for theoxidation of alkanes or a mixture of alkanes and alkenes to theircorresponding unsaturated carboxylic acids by vapor phase catalyticoxidation; to a method of making the catalyst; and to a process for thevapor phase catalytic oxidation of alkanes or a mixture of alkanes andalkenes to their corresponding unsaturated carboxylic acids.

[0002] The present invention also relates to a method of producingunsaturated nitrites by subjecting alkanes or a mixture of alkanes andalkenes to vapor phase catalytic oxidation in the presence of ammonia.

[0003] Nitriles, such as acrylonitrile and methacrylonitrile, have beenindustrially produced as important intermediates for the preparation offibers, synthetic resins, synthetic rubbers, and the like. The mostpopular method for producing such nitrites is to subject an olefin suchas propene or isobutene to a catalytic reaction with ammonia and oxygenin the presence of a catalyst in a gaseous phase at a high temperature.Known catalysts for conducting this reaction include a Mo—Bi—P—Ocatalyst, a V—Sb—O catalyst, an Sb—U—V—Ni—O catalyst, a Sb—Sn—W—Ocatalyst, a V—Sb—W—P—O catalyst and a catalyst obtained by mechanicallymixing a V—Sb—W—O oxide and a Bi—Ce—Mo—W—O oxide. However, in view ofthe price difference between propane and propene or between isobutaneand isobutene, attention has been drawn to the development of a methodfor producing acrylonitrile or methacrylonitrile by an ammoxidationreaction wherein a lower alkane, such as propane or isobutane, is usedas a starting material, and it is catalytically reacted with ammonia andoxygen in a gaseous phase in the presence of a catalyst.

[0004] In particular, U.S. Pat. No. 5,281,745 discloses a method forproducing an unsaturated nitrile comprising subjecting an alkane andammonia in the gaseous state to catalytic oxidation in the presence of acatalyst which satisfies the conditions:

[0005] (1) the mixed metal oxide catalyst is represented by theempirical formula

Mo_(a)V_(b)Te_(c)X_(x)O_(n)

[0006] wherein X is at least one element selected from the groupconsisting of niobium, tantalum, tungsten, titanium, aluminum,zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium,nickel, palladium, platinum, antimony, bismuth, boron and cerium and,when a =1, b=0.01 to 1.0, c=0.01 to 1.0, x=0.01 to 1.0 and n is a numbersuch that the total valency of the metal elements is satisfied; and

[0007] (2) the catalyst has X-ray diffraction peaks at the followingangles (±0.3°) of 2θ in its X-ray diffraction pattern: 22.1°, 28.2°,36.2°, 45.2° and 50.0°.

[0008] Similarly, Japanese Laid-Open Patent Application Publication No.6-228073 discloses a method of nitrile preparation comprising reactingan alkane in a gas phase contact reaction with ammonia in the presenceof a mixed metal oxide catalyst of the formula

W_(a)V_(b)Te_(c)X_(x)O_(n)

[0009] wherein X represents one or more elements selected from niobium,tantalum, titanium, aluminum, zirconium, chromium, manganese, iron,ruthenium, cobalt, rhodium, nickel, palladium, platinum, antimony,bismuth, indium and cerium and, when a=1, b=0.01 to 1.0, c=0.01 to 1.0,x=0.01 to 1.0 and n is determined by the oxide form of the elements.

[0010] U.S. Pat. No. 6,043,185 also discloses a catalyst useful in themanufacture of acrylonitrile or methacrylonitrile by the catalyticreaction in the vapor phase of a paraffin selected from propane andisobutane with molecular oxygen and ammonia by catalytic contact of thereactants in a reaction zone with a catalyst, wherein the catalyst hasthe empirical formula

Mo_(a)V_(b)Sb_(c)Ga_(d)X_(e)O_(x)

[0011] where X is one or more of As, Te, Se, Nb, Ta, W, Ti, Zr, Cr, Mn,Fe, Ru, Co, Rh, Ni, Pd, Pt, B, In, Ce, Re, Ir, Ge, Sn, Bi, Y, Pr, analkali metal and an alkaline earth metal; and when a=1, b=0.0 to 0.99,c=0.01 to 0.9, d=0.01 to 0.5, e=0.0 to 1.0 and x is determined by theoxidation state of the cations present.

[0012] Unsaturated carboxylic acids such as acrylic acid and methacrylicacid are industrially important as starting materials for varioussynthetic resins, coating materials and plasticizers. Commercially, thecurrent process for acrylic acid manufacture involves a two-stepcatalytic oxidation reaction starting with a propene feed. In the firststage, propene is converted to acrolein over a modified bismuthmolybdate catalyst. In the second stage, acrolein product from the firststage is converted to acrylic acid using a catalyst composed of mainlymolybdenum and vanadium oxides. In most cases, the catalyst formulationsare proprietary to the catalyst supplier, but, the technology is wellestablished. Moreover, there is an incentive to develop a single stepprocess to prepare the unsaturated acid from its corresponding alkene.Therefore, the prior art describes cases where complex metal oxidecatalysts are utilized for the preparation of unsaturated acid from acorresponding alkene in a single step.

[0013] European Published Patent Application No. 0 630 879 B1 disclosesa process for producing an unsaturated aldehyde and a carboxylic acidwhich comprises subjecting propene, isobutene or tertiary butanol to gasphase catalytic oxidation with molecular oxygen in the presence of (i) acatalyst composite oxide represented by the formula

Mo_(a)Bi_(b)Fe_(c)A_(d)B_(e)C_(f)D_(g)O_(x)

[0014] wherein A represents Ni and/or Co, B represents at least oneelement selected from Mn, Zn, Ca, Mg, Sn and Pb, C represents at leastone element selected from P, B, As, Te, W, Sb and Si, and D representsat least one element selected from K, Rb, Cs and T1; and wherein, whena=12, 0<b ≦10, 0<c≦10, 1<d≦10, 0≦e≦10, 0≦f≦20and 0≦g≦2, and x has avalue dependent on the oxidation state of the other elements; and (ii) amolybdenum oxide which in itself is substantially inert to said gasphase catalytic oxidation to provide the corresponding unsaturatedaldehyde and unsaturated carboxylic acid.

[0015] Japanese Laid-Open Patent Application Publication No. 07-053448discloses the manufacture of acrylic acid by the gas-phase catalyticoxidation of propene in the presence of mixed metal oxides containingMo, V, Te, O and X wherein X is at least one of Nb, Ta, W, Ti, Al, Zr,Cr, Mn, Fe, Ru, Co, Rh, Ni, Pd, Pt, Sb, Bi, B, In, Li, Na, K, Rb, Cs andCe.

[0016] Published International Application No. WO 00/09260 discloses acatalyst for selective oxidation of propene to acrylic acid and acroleincontaining a catalyst composition comprising the elements Mo, V, La, Pd,Nb and X in the following ratio:

Mo_(a)V_(b)La_(c)Pd_(d)Nb_(e)X_(f)

[0017] wherein X is Cu or Cr or a mixture thereof,

[0018] a is 1,

[0019] b is 0.01 to 0.9,

[0020] c is >0 to 0.2

[0021] d is 0.0000001 to 0.2,

[0022] e is 0 to 0.2, and

[0023] f is 0 to 0.2; and

[0024] wherein the numerical values of a, b, c, d, e and f represent therelative gram-atom ratios of the elements Mo, V, La, Pd, Nb and X,respectively, in the catalyst and the elements are present incombination with oxygen.

[0025] Commercial incentives also exist for producing acrylic acid usinga lower cost propane feed. Therefore, the prior art describes caseswherein a mixed metal oxide catalyst is used to convert propane toacrylic acid in one step.

[0026] U.S. Pat. No. 5,380,933 discloses a method for producing anunsaturated carboxylic acid comprising subjecting an alkane to a vaporphase catalytic oxidation reaction in the presence of a catalystcontaining a mixed metal oxide comprising, as essential components, Mo,V, Te, O and X, wherein X is at least one element selected from thegroup consisting of niobium, tantalum, tungsten, titanium, aluminum,zirconium, chromium, manganese, iron, ruthenium, cobalt, rhodium,nickel, palladium, platinum, antimony, bismuth, boron, indium andcerium; and wherein the proportions of the respective essentialcomponents, based on the total amount of the essential components,exclusive of oxygen, satisfy the following relationships:

[0027] 0.25<r(Mo)<0.98, 0.003<r(V)<0.5, 0.003<r(Te)<0.5 and0.003<r(X)<0.5, wherein r(Mo), r(V), r(Te) and r(X) are the molarfractions of Mo, V, Te and X, respectively, based on the total amount ofthe essential components exclusive of oxygen.

[0028] Published International Application No. WO 00/29106 discloses acatalyst for selective oxidation of propane to oxygenated productsincluding acrylic acid, acrolein and acetic acid, said catalyst systemcontaining a catalyst composition comprising

Mo_(a)V_(b)Ga_(c)Pd_(d)Nb_(e)X_(f)

[0029] wherein X is at least one element selected from La, Te, Ge, Zn,Si, In and W,

[0030] a is 1,

[0031] b is 0.01 to 0.9,

[0032] c is >0 to 0.2,

[0033] d is 0.0000001 to 0.2,

[0034] e is >0 to 0.2, and

[0035] f is 0.0 to 0.5; and

[0036] wherein the numerical values of a, b, c, d, e and f represent therelative gram-atom ratios of the elements Mo, V, Ga, Pd, Nb and X,respectively, in the catalyst and the elements are present incombination with oxygen.

[0037] Japanese Laid-Open Patent Application Publication No. 2000-037623discloses a method for producing an unsaturated carboxylic acidcomprising subjecting an alkane to a vapor phase catalytic oxidation inthe presence of a catalyst having the empirical formula

MoV_(a)Nb_(b)X_(c)Z_(d)O_(n)

[0038] wherein X is at least one element selected from the groupconsisting of Te and Sb, Z is at least one element selected from thegroup consisting of W, Cr, Ta, Ti, Zr, Hf. Mn, Re, Fe, Ru, Co, Rh, Ni,Pd, Pt, Ag, Zn, B, Al, Ga, In, Ge, Sn, Pb, P, Bi, Y, rare earth elementsand alkaline earth elements, 0.1≦a ≦1.0, 0.01≦b≦1.0, 0.01≦c≦1.0, 0≦d≦1.0and n is determined by the oxidation states of the other elements.

[0039] Despite the above-noted attempts to provide new and improvedcatalysts for the oxidation of alkanes to unsaturated carboxylic acidsand for the ammoxidation of alkanes to unsaturated nitrites, oneimpediment to the provision of a commercially viable process for suchcatalytic oxidations is the identification of a catalyst providingadequate conversion and suitable selectivity, thereby providingsufficient yield of the unsaturated product.

[0040] By the present invention, there are provided promoted catalystswherein the selectivity is greatly enhanced as to the base catalyst and,hence, the overall yield of the desired reaction product is also greatlyenhanced. Moreover, with respect to the combined use of Ir and Sm, theyields of CO and CO₂ are much lower than for the base catalyst alongwith the CO/CO₂ ratio.

[0041] Thus, in a first aspect, the present invention provides acatalyst comprising a promoted mixed metal oxide having the empiricalformula

A_(a)M_(b)N_(c)X_(d)Ir_(e)Sm_(f)O_(g)

[0042] wherein A is at least one element selected from the groupconsisting of Mo and W, M is at least one element selected from thegroup consisting of V and Ce, N is at least one element selected fromthe group consisting of Te, Sb and Se, and X is at least one elementselected from the group consisting of Nb, Ta, Ti, Al, Zr, Cr, Mn, Fe,Ru, Co, Rh, Ni, Pt, Sb, Bi, B, In, As, Ge, Sn, Li, Na, K, Rb, Cs, Fr,Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb, P, Pm, Eu, Gd, Dy, Ho, Er, Tm, Yb andLu; and

[0043] wherein, when a=1, b=0.01 to 1.0, c=0.01 to 1.0, d=0.01 to 1.0,e=0 or 0.001 to 0.1, f=0 or 0.001 to 0.1 and g is dependent on theoxidation state of the other elements, with the proviso that e and fcannot simultaneously be 0.

[0044] In a second aspect, the present invention provides a process forproducing an unsaturated carboxylic acid, which comprises subjecting analkane or a mixture of an alkane and an alkene to a vapor phasecatalytic oxidation reaction in the presence of a catalyst containing apromoted mixed metal oxide having the empirical formula

A_(a)M_(b)N_(c)X_(d)Ir_(e)Sm_(f)O_(g)

[0045] wherein A is at least one element selected from the groupconsisting of Mo and W, M is at least one element selected from thegroup consisting of V and Ce, N is at least one element selected fromthe group consisting of Te, Sb and Se, and X is at least one elementselected from the group consisting of Nb, Ta, Ti, Al, Zr, Cr, Mn, Fe,Ru, Co, Rh, Ni, Pt, Sb, Bi, B, In, As, Ge, Sn, Li, Na, K, Rb, Cs, Fr,Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb, P, Pm, Eu, Gd, Dy, Ho, Er, Tm, Yb andLu; and

[0046] wherein, when a=1, b=0.01 to 1.0, c=0.01 to 1.0, d=0.01 to 1.0,e=0 or 0.001 to 0.1, f=0 or 0.001 to 0.1 and g is dependent on theoxidation state of the other elements, with the proviso that e and fcannot simultaneously be 0.

[0047] In a third aspect, the present invention provides a process forproducing an unsaturated nitrile, which comprises subjecting an alkane,or a mixture of an alkane and an alkene, and ammonia to a vapor phasecatalytic oxidation reaction in the presence of a catalyst containing apromoted mixed metal oxide having the empirical formula

A_(a)M_(b)N_(c)X_(d)Ir_(e)Sm_(f)O_(g)

[0048] wherein A is at least one element selected from the groupconsisting of Mo and W, M is at least one element selected from thegroup consisting of V and Ce, N is at least one element selected fromthe group consisting of Te, Sb and Se, and X is at least one elementselected from the group consisting of Nb, Ta, Ti, Al, Zr, Cr, Mn, Fe,Ru, Co, Rh, Ni, Pt, Sb, Bi, B, In, As, Ge, Sn, Li, Na, K, Rb, Cs, Fr,Be, Mg, Ca, Sr, Ba, Ra, Hf. Pb, P, Pm, Eu, Gd, Dy, Ho, Er, Tm, Yb andLu; and

[0049] wherein, when a=1, b=0.01 to 1.0, c=0.01 to 1.0, d=0.01 to 1.0,e=0 or 0.001 to 0.1, f=0 or 0.001 to 0.1 and g is dependent on theoxidation state of the other elements, with the proviso that e and fcannot simultaneously be 0.

[0050] In a fourth aspect, the present invention provides a catalystproduced by the process comprising:

[0051] (1) admixing compounds of the elements A, M, N, X, Ir and Sm andat least one solvent to form an admixture, wherein A is at least oneelement selected from the group consisting of Mo and W, M is at leastone element selected from the group consisting of V and Ce, N is atleast one element selected from the group consisting of Te, Sb and Se,and X is at lest one element selected from the group consisting of Nb,Ta, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pt, Bi, B, In, As, Ge, Sn,Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb, P, Pm, Eu, Gd,Dy, Ho, Er, Tm, Yb and Lu, and wherein the elements A, M, N, X, Ir andSm are present in such amounts that the atomic ratio of A:M:N:X:Ir:Sm isa:b:c:d:e:f and, when a=1,b=0.01 to 1.0, c=0.01 to 1.0, d=0.01 to 1.0,e=0 or 0.001 to 0.1 and f=0 or 0.001 to 0.1, with the proviso that e andf cannot simultaneously be 0;

[0052] (2) removing said at least one solvent from the admixture toobtain a catalyst precursor; and

[0053] (3) calcining said catalyst precursor.

[0054] In the case where the initial admixture did not contain one of Iror Sm (i.e., e was 0 or f was 0), the missing element may besubsequently added, if so desired. In this regard, the process forproducing the catalyst may further comprise:

[0055] (4) admixing a compound of Sm (or Ir), said calcined catalystprecursor and at least one solvent to form a second admixture;

[0056] (5) removing said at least one solvent from the second admixtureto obtain a second catalyst precursor; and

[0057] (6) calcining said second catalyst precursor.

[0058] In a fifth aspect, the present invention provides a process forproducing an unsaturated carboxylic acid, which comprises subjecting analkane or a mixture of an alkane and an alkene to a vapor phasecatalytic oxidation reaction in the presence of the catalyst produced bythe process comprising:

[0059] (1) admixing compounds of the elements A, M, N, X, Ir and Sm andat least one solvent to form an admixture, wherein A is at least oneelement selected from the group consisting of Mo and W, M is at leastone element selected from the group consisting of V and Ce, N is atleast one element selected from the group consisting of Te, Sb and Se,and X is at lest one element selected from the group consisting of Nb,Ta, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pt, Bi, B, In, As, Ge, Sn,Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb, P, Pm, Eu, Gd,Dy, Ho, Er, Tm, Yb and Lu, and wherein the elements A, M, N, X, Ir andSm are present in such amounts that the atomic ratio of A:M:N:X:Ir:Sm isa:b:c:d:e:f and, when a=1, b=0.01 to 1.0, c=0.01 to 1.0,d=0.01 to 1.0,e=0 or 0.001 to 0.1 and f=0 or 0.001 to 0.1, with the proviso that e andf cannot simultaneously be 0;

[0060] (2) removing said at least one solvent from the admixture toobtain a catalyst precursor; and

[0061] (3) calcining said catalyst precursor.

[0062] In a sixth aspect, the present invention provides a process forproducing an unsaturated nitrile, which comprises subjecting an alkane,or a mixture of an alkane and an alkene, and ammonia to a vapor phasecatalytic oxidation reaction in the presence of the catalyst produced bythe process comprising:

[0063] (1) admixing compounds of the elements A, M, N, X, Ir and Sm andat least one solvent to form an admixture, wherein A is at least oneelement selected from the group consisting of Mo and W, M is at leastone element selected from the group consisting of V and Ce, N is atleast one element selected from the group consisting of Te, Sb and Se,and X is at lest one element selected from the group consisting of Nb,Ta, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pt, Bi, B, In, As, Ge, Sn,Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb, P, Pm, Eu, Gd,Dy, Ho, Er, Tm, Yb and Lu, and wherein the elements A, M, N, X, Ir andSm are present in such amounts that the atomic ratio of A:M:N:X:Ir:Sm isa:b:c:d:e:f and, when a=1, b=0.01 to 1.0, c=0.01 to 1.0, d=0.01 to 1.0,e=0 or 0.001 to 0.1 and f=0 or 0.001 to 0.1, with the proviso that e andf cannot simultaneously be 0;

[0064] (2) removing said at least one solvent from the admixture toobtain a catalyst precursor; and

[0065] (3) calcining said catalyst precursor.

[0066] The promoted mixed metal oxide to be used as a catalyst componentof the present invention has the empirical formula

A_(a)M_(b)N_(c)X_(d)Ir_(e)Sm_(f)O_(g)

[0067] wherein A is at least one element selected from the groupconsisting of Mo and W, M is at least one element selected from thegroup consisting of V and Ce, N is at least one element selected fromthe group consisting of Te, Sb and Se, and X is at least one elementselected from the group consisting of Nb, Ta, Ti, Al, Zr, Cr, Mn, Fe,Ru, Co, Rh, Ni, Pt, Sb, Bi, B, In, As, Ge, Sn, Li, Na, K, Rb, Cs, Fr,Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb, P, Pm, Eu, Gd, Dy, Ho, Er, Tm, Yb andLu; and

[0068] wherein, when a=1, b=0.01 to 1.0, c=0.01 to 1.0, d=0.01 to 1.0,e=0 or 0.001 to 0.1, f=0 or 0.001 to 0.1 and g is dependent on theoxidation state of the other elements, with the proviso that e and fcannot simultaneously be 0.

[0069] Preferably, when a=1, b=0.1 to 0.5, c=0.05 to 0.5, d=0.01 to 0.5,e=0.001 to 0.02, and f=0.001 to 0.02. More preferably, when a=1, b=0.15to 0.45, c=0.05 to 0.45, d =0.01 to 0.1, e=0.002 to 0.01, and f=0.002 to0.01. However, in an alternative embodiment, when a=1 and f=0, b=0.01 to1.0, c=0.01 to 1.0, d=0.01 to 1.0 and e=0.001 to 0.1; preferably, whena=1 and f=0, b=0.1 to 0.5, c=0.05 to 0.5, d=0.01 to 0.5 and e=0.002 to0.04; more preferably, when a=1 and f=0, b=0.15 to 0.45, c=0.05 to 0.45.d=0.01 to 0.1 and e=0.005 to 0.02. Moreover in a fuirther alternativeembodiment, when a=1 and e=0, b=0.01 to 1.0, c=0.01 to 1.0, d=0.01 to1.0and f=0.001 to 0.1; preferably, when a=1 and e=0, b=0.1 to 0.5,c=0.05 to 0.5, d=0.01 to 0.5 and f=0.002 to 0.04; more preferably, whena=1 and e=0, b=0.15 to 0.45, c=0.05 to 0.45. d=0.01 to 0.1 and f=0.005to 0.02.

[0070] The value of g, i.e. the amount of oxygen present, is dependenton the oxidation state of the other elements in the catalyst. However, gis typically in the range of from 3 to 4.7.

[0071] Preferred promoted mixed metal oxides have the empirical formulaeMo_(a)V_(b)Te_(c)Nb_(d)Ir_(e)Sm_(f)O_(g) andW_(a)V_(b)Te_(c)Nb_(d)Ir_(e)Sm_(f)O_(g) wherein a, b, c, d, e, f and gare as previously defined.

[0072] Further, as the promoted mixed metal oxide, one having a certainspecific crystal structure is preferred. Specifically, preference isgiven to the one which exhibits the following five main diffractionpeaks at specific diffraction angles 2θ in the X-ray diffraction patternof the promoted mixed metal oxide (as measured using Cu-Kα radiation asthe source): X-ray lattice plane Diffraction angle 2θ Spacing mediumRelative (±0.3°) (Å) intensity 22.1° 4.02 100 28.2° 3.16 20˜150 36.2°2.48 5˜60 45.2° 2.00 2˜40 50.0° 1.82 2˜40

[0073] The intensity of the X-ray diffraction peaks may vary upon themeasuring of each crystal. However, the intensity, relative to the peakintensity at 22.1°0 being 100, is usually within the above ranges.Generally, the peak intensities at 2θ=22.1° and 28.2° are distinctlyobserved. However, so long as the above five diffraction peaks areobservable, the basic crystal structure is the same even if other peaksare observed in addition to the five diffraction peaks, and such astructure is useful for the present invention.

[0074] The promoted mixed metal oxide can be prepared in the followingmanner.

[0075] In a first step a slurry or solution may be formed by admixingmetal compounds, preferably at least one of which contains oxygen, andat least one solvent in appropriate amounts to form the slurry orsolution. Preferably, a solution is formed at this stage of the catalystpreparation. Generally, the metal compounds contain elements A, M, N, X,Ir, Sm and O, as previously defined.

[0076] Suitable solvents include water; alcohols including , but notlimited to, methanol, ethanol, propanol, and diols, etc.; as well asother polar solvents known in the art. Generally, water is preferred.The water is any water suitable for use in chemical syntheses including,without limitation, distilled water and de-ionized water. The amount ofwater present is preferably an amount sufficient to keep the elementssubstantially in solution long enough to avoid or minimize compositionaland/or phase segregation during the preparation steps. Accordingly, theamount of water will vary according to the amounts and solubilities ofthe materials combined. However, as stated above, the amount of water ispreferably sufficient to ensure an aqueous solution is formed , and nota slurry, at the time of mixing.

[0077] For example, when a mixed metal oxide of the formulaMo_(a)V_(b)Te_(c)Nb_(d)Ir_(e)Sm_(f)O_(g) wherein the element A is Mo,the element M is V, the element N is Te and the element X is Nb, is tobe prepared, an aqueous solution of niobium oxalate may be added to anaqueous solution or slurry of ammonium heptamolybdate, ammoniummetavanadate, telluric acid, iridium and/or samarium so that the atomicratio of the respective metal elements would be in the prescribedproportions.

[0078] Once the aqueous slurry or solution (preferably a solution) isformed, the water is removed by any suitable method, known in the art,to form a catalyst precursor. Such methods include, without limitation,vacuum drying, freeze drying, spray drying, rotary evaporation and airdrying. Vacuum drying is generally performed at pressures ranging from10 mmHg to 500 mmHg. Freeze drying typically entails freezing the slurryor solution, using, for instance, liquid nitrogen, and drying the frozenslurry or solution under vacuum. Spray drying is generally performedunder an inert atmosphere such as nitrogen or argon, with an inlettemperature ranging from 125° C. to 200° C. and an outlet temperatureranging from 75° C. to 150° C. Rotary evaporation is generally performedat a bath temperature of from 25° C. to 90° C. and at a pressure of from10 mmHg to 760 mmHg, preferably at a bath temperature of from 40° to 90°C. and at a pressure of from 10 mmHg to 350 mmHg, more preferably at abath temperature of from 40° C. to 60° C. and at a pressure of from 10mmHg to 40 mmHg. Air drying may be effected at temperatures ranging from25° C. to 90° C. Rotary evaporation or air drying are generallypreferred.

[0079] Once obtained, the catalyst precursor is calcined. Thecalcination may be conducted in an oxygen-containing atmosphere or inthe substantial absence of oxygen, e.g., in an inert atmosphere or invacuo. The inert atmosphere may be any material which is substantiallyinert, i.e., does not react or interact with, the catalyst precursor.Suitable examples include, without limitation, nitrogen, argon, xenon,helium or mixtures thereof. Preferably, the inert atmosphere is argon ornitrogen. The inert atmosphere may flow over the surface of the catalystprecursor or may not flow thereover (a static environment). When theinert atmosphere does flow over the surface of the catalyst precursor,the flow rate can vary over a wide range, e.g., at a space velocity offrom 1 to 500 hr⁻¹. The calcination is usually performed at atemperature of from 350° C. to 850° C., preferably from 400° C. to 700°C., more preferably from 500° C. to 640° C. The calcination is performedfor an amount of time suitable to form the aforementioned catalyst.Typically, the calcination is performed for from 0.5 to 30 hours,preferably from 1 to 25 hours, more preferably for from 1 to 15 hours,to obtain the desired promoted mixed metal oxide.

[0080] In a preferred mode of operation, the catalyst precursor iscalcined in two stages. In the first stage, the catalyst precursor iscalcined in an oxidizing environment (e.g. air) at a temperature of from200° C. to 400° C., preferably from 275° C. to 325° C. for from 15minutes to 8 hours, preferably for from 1 to 3 hours. In the secondstage, the material from the first stage is calcined in a non-oxidizingenvironment (e.g., an inert atmosphere) at a temperature of from 500° C.to 750° C., preferably for from 550° C. to 650° C., for 15 minutes to 8hours, preferably for from 1 to 3 hours. Optionally, a reducing gas,such as, for example, ammonia or hydrogen, may be added during thesecond stage calcination.

[0081] In a particularly preferred mode of operation, the catalystprecursor in the first stage is placed in the desired oxidizingatmosphere at room temperature and then raised to the first stagecalcination temperature and held there for the desired first stagecalcination time. The atmosphere is then replaced with the desirednon-oxidizing atmosphere for the second stage calcination, thetemperature is raised to the desired second stage calcinationtemperature and held there for the desired second stage calcinationtime.

[0082] In the previously discussed case, where the initial mixture doesnot contain one of Ir and Sm, and where the missing element issubsequently added, the second admixture may be formed by the sametechniques as noted above. Similarly, the removal of the at least one asolvent, to form a second catalyst precursor, and the calcination of thesecond catalyst precursor, may be effected in the same manners as setforth above.

[0083] Although any type of heating mechanism, e.g., a furnace, may beutilized during the calcination, it is preferred to conduct thecalcination under a flow of the designated gaseous environment.Therefore, it is advantageous to conduct the calcination in a bed withcontinuous flow of the desired gas(es) through the bed of solid catalystprecursor particles.

[0084] With calcination, a catalyst is formed having the formulaA_(a)M_(b)N_(c)X_(d)Ir_(e)Sm_(f)O_(g) wherein A, M, N, X, O, a, b, c, d,e, f and g are as previously defined.

[0085] The starting materials for the above promoted mixed metal oxideare not limited to those described above. A wide range of materialsincluding, for example, oxides, nitrates, halides or oxyhalides,alkoxides, acetylacetonates, and organometallic compounds may be used.For example, ammonium heptamolybdate may be utilized for the source ofmolybdenum in the catalyst. However, compounds such as MoO₃, MoO₂,MoCl₅, MoOCl₄, Mo(OC₂H₅)₅, molybdenum acetylacetonate, phosphomolybdicacid and silicomolybdic acid may also be utilized instead of ammoniumheptamolybdate. Similarly, ammonium metavanadate may be utilized for thesource of vanadium in the catalyst. However, compounds such as V₂O₅,V₂O₃, VOCl₃, VCl₄, VO(OC₂H₅)₃, vanadium acetylacetonate and vanadylacetylacetonate may also be utilized instead of ammonium metavanadate.The tellurium source may include telluric acid, TeCl₄, Te(OC₂H₅)₅,Te(OCH(CH₃)₂)₄ and TeO₂. The niobium source may include ammonium niobiumoxalate, Nb₂O₅, NbCl₅, niobic acid or Nb(OC₂H₅)₅ as well as the moreconventional niobium oxalate. The iridium source may be iridiumacetylacetonate, iridium bromide hydrate, iridium chloride, iridiumchloride hydrochloride hydrate, iridium chloride hydrate, iridium oxide,iridium oxide hydrate, iridium oxoacetate trihydrate or iridiumdissolved in an aqueous inorganic acid, e.g., nitric acid. The samriumsource may be samarium (III) acetate hydrate, samarium (III)acetylacetonate hydrate, samarium (II) bromide, samarium (III) bromide,samarium (III) bromide hexahydrate, samarium (III) carbonate hydrate,samarium (II) chloride, samarium (III) chloride, samarium (III) chloridehexahydrate, samarium (III) fluoride, samarium (II) iodide, samarium(III) iodide, damarium (III) isopropoxide, samarium (III) nitratehexahydrate, samarium (III) oxalate hydrate, samarium (III) oxide or asolution of samarium in an aqueous inorganic acid, e.g., nitric acid

[0086] A promoted mixed metal oxide, thus obtained, exhibits excellentcatalytic activities by itself. However, the promoted mixed metal oxidecan be converted to a catalyst having higher activities by grinding.

[0087] There is no particular restriction as to the grinding method, andconventional methods may be employed. As a dry grinding method, a methodof using a gas stream grinder may, for example, be mentioned whereincoarse particles are permitted to collide with one another in a highspeed gas stream for grinding. The grinding may be conducted not onlymechanically but also by using a mortar or the like in the case of asmall scale operation.

[0088] As a wet grinding method wherein grinding is conducted in a wetstate by adding water or an organic solvent to the above mixed metaloxide, a conventional method of using a rotary cylinder-type medium millor a medium-stirring type mill, may be mentioned. The rotarycylinder-type medium mill is a wet mill of the type wherein a containerfor the object to be ground is rotated, and it includes, for example, aball mill and a rod mill. The medium-stirring type mill is a wet mill ofthe type wherein the object to be ground, contained in a container isstirred by a stirring apparatus, and it includes, for example, a rotaryscrew type mill, and a rotary disc type mill.

[0089] The conditions for grinding may suitably be set to meet thenature of the above-mentioned promoted mixed metal oxide, the viscosity,the concentration, etc. of the solvent used in the case of wet grinding,or the optimum conditions of the grinding apparatus. However, it ispreferred that grinding is conducted until the average particle size ofthe ground catalyst precursor would usually be at most 20 μm, morepreferably at most 5 μm. Improvement in the catalytic performance mayoccur due to such grinding.

[0090] Further, in some cases, it is possible to further improve thecatalytic activities by further adding a solvent to the ground catalystprecursor to form a solution or slurry, followed by drying again. Thereis no particular restriction as to the concentration of the solution orslurry, and it is usual to adjust the solution or slurry so that thetotal amount of the starting material compounds for the ground catalystprecursor is from 10 to 60 wt %. Then, this solution or slurry is driedby a method such as spray drying, freeze drying, evaporation to drynessor vacuum drying, preferably by the spray drying method. Further,similar drying may be conducted also in the case where wet grinding isconducted.

[0091] The oxide obtained by the above-mentioned method may be used as afinal catalyst, but it may further be subjected to heat treatmentusually at a temperature of from 200° to 700° C. for from 0.1 to 10hours.

[0092] The promoted mixed metal oxide thus obtained may be used byitself as a solid catalyst, but may be formed into a catalyst togetherwith a suitable carrier such as silica, alumina, titania,aluminosilicate, diatomaceous earth or zirconia. Further, it may bemolded into a suitable shape and particle size depending upon the scaleor system of the reactor.

[0093] Alternatively, the metal components of the presently contemplatedcatalyst may be supported on materials such as alumina, silica,silica-alumina, zirconia, titania, etc. by conventional incipientwetness techniques. In one typical method, solutions containing themetals are contacted with the dry support such that the support iswetted; then, the resultant wetted material is dried, for example, at atemperature from room temperature to 200° C. followed by calcination asdescribed above. In another method, metal solutions are contacted withthe support, typically in volume ratios of greater than 3:1 (metalsolution:support), and the solution agitated such that the metal ionsare ion-exchanged onto the support. The metal-containing support is thendried and calcined as detailed above.

[0094] In its second aspect, the present invention provides a processfor producing an unsaturated carboxylic acid, which comprises subjectingan alkane, or a mixture of an alkane and an alkene, to a vapor phasecatalytic oxidation reaction in the presence of a catalyst containingthe above promoted mixed metal oxide, to produce an unsaturatedcarboxylic acid.

[0095] In the production of such an unsaturated carboxylic acid, it ispreferred to employ a starting material gas which contains steam. Insuch a case, as a starting material gas to be supplied to the reactionsystem, a gas mixture comprising a steam-containing alkane, or asteam-containing mixture of alkane and alkene, and an oxygen-containinggas, is usually used. However, the steam-containing alkane, or thesteam-containing mixture of alkane and alkene, and the oxygen-containinggas may be alternately supplied to the reaction system. The steam to beemployed may be present in the form of steam gas in the reaction system,and the manner of its introduction is not particularly limited.

[0096] Further, as a diluting gas, an inert gas such as nitrogen, argonor helium may be supplied. The molar ratio (alkane or mixture of alkaneand alkene):(oxygen):(diluting gas): (H₂O) in the starting material gasis preferably (1):(0.1 to 10):(0 to 20):(0.2 to 70), more preferably(1):(1 to 5.0):(0 to 10):(5 to 40).

[0097] When steam is supplied together with the alkane, or the mixtureof alkane and alkene, as starting material gas, the selectivity for anunsaturated carboxylic acid is distinctly improved, and the unsaturatedcarboxylic acid can be obtained from the alkane, or mixture of alkaneand alkene, in good yield simply by contacting in one stage. However,the conventional technique utilizes a diluting gas such as nitrogen,argon or helium for the purpose of diluting the starting material. Assuch a diluting gas, to adjust the space velocity, the oxygen partialpressure and the steam partial pressure, an inert gas such as nitrogen,argon or helium may be used together with the steam.

[0098] As the starting material alkane it is preferred to employ aC₃₋₈alkane, particularly propane, isobutane or n-butane; morepreferably, propane or isobutane; most preferably, propane. According tothe present invention, from such an alkane, an unsaturated carboxylicacid such as an α,β-unsaturated carboxylic acid can be obtained in goodyield. For example, when propane or isobutane is used as the startingmaterial alkane, acrylic acid or methacrylic acid will be obtained,respectively, in good yield.

[0099] In the present invention, as the starting material mixture ofalkane and alkene, it is preferred to employ a mixture of C₃₋₈alkane andC₃₋₈alkene, particularly propane and propene, isobutane and isobutene orn-butane and n-butene. As the starting material mixture of alkane andalkene, propane and propene or isobutane and isobutene are morepreferred. Most preferred is a mixture of propane and propene. Accordingto the present invention, from such a mixture of an alkane and analkene, an unsaturated carboxylic acid such as an α,β-unsaturatedcarboxylic acid can be obtained in good yield. For example, when propaneand propene or isobutane and isobutene are used as the starting materialmixture of alkane and alkene, acrylic acid or methacrylic acid will beobtained, respectively, in good yield. Preferably, in the mixture ofalkane and alkene, the alkene is present in an amount of at least 0.5%by weight, more preferably at least 1.0% by weight to 95% by weight;most preferably, 3% by weight to 90% by weight.

[0100] As an alternative, an alkanol, such as isobutanol, which willdehydrate under the reaction conditions to form its correspondingalkene, i.e. isobutene, may also be used as a feed to the presentprocess or in conjunction with the previously mentioned feed streams.

[0101] The purity of the starting material alkane is not particularlylimited, and an alkane containing a lower alkane such as methane orethane, air or carbon dioxide, as impurities, may be used without anyparticular problem. Further, the starting material alkane may be amixture of various alkanes. Similarly, the purity of the startingmaterial mixture of alkane and alkene is not particularly limited, and amixture of alkane and alkene containing a lower alkene such as ethene, alower alkane such as methane or ethane, air or carbon dioxide, asimpurities, may be used without any particular problem. Further, thestarting material mixture of alkane and alkene may be a mixture ofvarious alkanes and alkenes.

[0102] There is no limitation on the source of the alkene. It may bepurchased, per se, or in admixture with an alkane and/or otherimpurities. Alternatively, it can be obtained as a by-product of alkaneoxidation. Similarly, there is no limitation on the source of thealkane. It may be purchased, per se, or in admixture with an alkeneand/or other impurities. Moreover, the alkane, regardless of source, andthe alkene, regardless of source, may be blended as desired.

[0103] The detailed mechanism of the oxidation reaction of the presentinvention is not clearly understood, but the oxidation reaction iscarried out by oxygen atoms present in the above promoted mixed metaloxide or by molecular oxygen present in the feed gas. To incorporatemolecular oxygen into the feed gas, such molecular oxygen may be pureoxygen gas. However, it is usually more economical to use anoxygen-containing gas such as air, since purity is not particularlyrequired.

[0104] It is also possible to use only an alkane, or a mixture of alkaneand alkene, substantially in the absence of molecular oxygen for thevapor phase catalytic reaction. In such a case, it is preferred to adopta method wherein a part of the catalyst is appropriately withdrawn fromthe reaction zone from time to time, then sent to an oxidationregenerator, regenerated and then returned to the reaction zone forreuse. As the regeneration method of the catalyst, a method may, forexample, be mentioned which comprises contacting an oxidative gas suchas oxygen, air or nitrogen monoxide with the catalyst in the regeneratorusually at a temperature of from 300° to 600° C.

[0105] The second aspect of the present invention will be described infurther detail with respect to a case where propane is used as thestarting material alkane and air is used as the oxygen source. Thereaction system may be a fixed bed system or a fluidized bed system.However, since the reaction is an exothermic reaction, a fluidized bedsystem may preferably be employed whereby it is easy to control thereaction temperature. The proportion of air to be supplied to thereaction system is important for the selectivity for the resultingacrylic acid, and it is usually at most 25 moles, preferably from 0.2 to18 moles per mole of propane, whereby high selectivity for acrylic acidcan be obtained. This reaction can be conducted usually underatmospheric pressure, but may be conducted under a slightly elevatedpressure or slightly reduced pressure. With respect to other alkanessuch as isobutane, or to mixtures of alkanes and alkenes such as propaneand propene, the composition of the feed gas may be selected inaccordance with the conditions for propane.

[0106] Typical reaction conditions for the oxidation of propane orisobutane to acrylic acid or methacrylic acid may be utilized in thepractice of the present invention. The process may be practiced in asingle pass mode (only fresh feed is fed to the reactor) or in a recyclemode (at least a portion of the reactor effluent is returned to thereactor). General conditions for the process of the present inventionare as follows: the reaction temperature can vary from 200° C. to 700°C., but is usually in the range of from 200° C. to 550° C., morepreferably 250° C. to 480° C., most preferably 300° C. to 400° C.; thegas space velocity, SV, in the vapor phase reactor is usually within arange of from 100 to 10,000 hr⁻¹, preferably 300 to 6,000 hr⁻¹, morepreferably 300 to 2,000 hr⁻¹; the average contact time with the catalystcan be from 0.01 to 10 seconds or more, but is usually in the range offrom 0.1 to 10 seconds, preferably from 2 to 6 seconds; the pressure inthe reaction zone usually ranges from 0 to 75 psig, but is preferably nomore than 50 psig. In a single pass mode process, it is preferred thatthe oxygen be supplied from an oxygen-containing gas such as air. Thesingle pass mode process may also be practiced with oxygen addition. Inthe practice of the recycle mode process, oxygen gas by itself is thepreferred source so as to avoid the build up of inert gases in thereaction zone.

[0107] Of course, in the oxidation reaction of the present invention, itis important that the hydrocarbon and oxygen concentrations in the feedgases be maintained at the appropriate levels to minimize or avoidentering a flammable regime within the reaction zone or especially atthe outlet of the reactor zone. Generally, it is preferred that theoutlet oxygen levels be low to both minimize after-burning and,particularly, in the recycle mode of operation, to minimize the amountof oxygen in the recycled gaseous effluent stream. In addition,operation of the reaction at a low temperature (below 450° C.) isextremely attractive because after-burning becomes less of a problemwhich enables the attainment of higher selectivity to the desiredproducts. The catalyst of the present invention operates moreefficiently at the lower temperature range set forth above,significantly reducing the formation of acetic acid and carbon oxides,and increasing selectivity to acrylic acid. As a diluting gas to adjustthe space velocity and the oxygen partial pressure, an inert gas such asnitrogen, argon or helium may be employed.

[0108] When the oxidation reaction of propane, and especially theoxidation reaction of propane and propene, is conducted by the method ofthe present invention, carbon monoxide, carbon dioxide, acetic acid,etc. may be produced as by-products, in addition to acrylic acid.Further, in the method of the present invention, an unsaturated aldehydemay sometimes be formed depending upon the reaction conditions. Forexample, when propane is present in the starting material mixture,acrolein may be formed; and when isobutane is present in the startingmaterial mixture, methacrolein may be formed. In such a case, such anunsaturated aldehyde can be converted to the desired unsaturatedcarboxylic acid by subjecting it again to the vapor phase catalyticoxidation with the promoted mixed metal oxide-containing catalyst of thepresent invention or by subjecting it to a vapor phase catalyticoxidation reaction with a conventional oxidation reaction catalyst foran unsaturated aldehyde.

[0109] In its third aspect, the method of the present inventioncomprises subjecting an alkane, or a mixture of an alkane and an alkene,to a vapor phase catalytic oxidation reaction with ammonia in thepresence of a catalyst containing the above mixed metal oxide, toproduce an unsaturated nitrile.

[0110] In the production of such an unsaturated nitrile, as the startingmaterial alkane, it is preferred to employ a C₃₋₈alkane such as propane,butane, isobutane, pentane, hexane and heptane. However, in view of theindustrial application of nitrites to be produced, it is preferred toemploy a lower alkane having 3 or 4 carbon atoms, particularly propaneand isobutane.

[0111] Similarly, as the starting material mixture of alkane and alkene,it is preferred to employ a mixture of C₃₋₈alkane and C₃₋₈alkene such aspropane and propene, butane and butene, isobutane and isobutene, pentaneand pentene, hexane and hexene, and heptane and heptene. However, inview of the industrial application of nitrites to be produced, it ismore preferred to employ a mixture of a lower alkane having 3 or 4carbon atoms and a lower alkene having 3 or 4 carbon atoms, particularlypropane and propene or isobutane and isobutene. Preferably, in themixture of alkane and alkene, the alkene is present in an amount of atleast 0.5% by weight, more preferably at least 1.0% by weight to 95% byweight, most preferably 3% by weight to 90% by weight.

[0112] The purity of the starting material alkane is not particularlylimited, and an alkane containing a lower alkane such as methane orethane, air or carbon dioxide, as impurities, may be used without anyparticular problem. Further, the starting material alkane may be amixture of various alkanes. Similarly, the purity of the startingmaterial mixture of alkane and alkene is not particularly limited, and amixture of alkane and alkene containing a lower alkene such as ethene, alower alkane such as methane or ethane, air or carbon dioxide, asimpurities, may be used without any particular problem. Further, thestarting material mixture of alkane and alkene may be a mixture ofvarious alkanes and alkenes.

[0113] There is no limitation on the source of the alkene. It may bepurchased, per se, or in admixture with an alkane and/or otherimpurities. Alternatively, it can be obtained as a by-product of alkaneoxidation. Similarly, there is no limitation on the source of thealkane. It may be purchased, per se, or in admixture with an alkeneand/or other impurities. Moreover, the alkane, regardless of source, andthe alkene, regardless of source, may be blended as desired.

[0114] The detailed mechanism of the ammoxidation reaction of thisaspect of the present invention is not clearly understood. However, theoxidation reaction is conducted by the oxygen atoms present in the abovepromoted mixed metal oxide or by the molecular oxygen in the feed gas.When molecular oxygen is incorporated in the feed gas, the oxygen may bepure oxygen gas. However, since high purity is not required, it isusually economical to use an oxygen-containing gas such as air.

[0115] As the feed gas, it is possible to use a gas mixture comprisingan alkane, or a mixture of an alkane and an alkene, ammonia and anoxygen-containing gas, However, a gas mixture comprising an alkane or amixture of an alkane and an alkene and ammonia, and an oxygen-containinggas may be supplied alternately.

[0116] When the gas phase catalytic reaction is conducted using analkane, or a mixture of an alkane and an alkene, and ammoniasubstantially free from molecular oxygen, as the feed gas, it isadvisable to employ a method wherein a part of the catalyst isperiodically withdrawn and sent to an oxidation regenerator forregeneration, and the regenerated catalyst is returned to the reactionzone. As a method for regenerating the catalyst, a method may bementioned wherein an oxidizing gas such as oxygen, air or nitrogenmonoxide is permitted to flow through the catalyst in the regeneratorusually at a temperature of from 300° C. to 600° C.

[0117] The third aspect of the present invention will be described infurther detail with respect to a case where propane is used as thestarting material alkane and air is used as the oxygen source. Theproportion of air to be supplied for the reaction is important withrespect to the selectivity for the resulting acrylonitrile. Namely, highselectivity for acrylonitrile is obtained when air is supplied within arange of at most 25 moles, particularly 1 to 15 moles, per mole of thepropane. The proportion of ammonia to be supplied for the reaction ispreferably within a range of from 0.2 to 5 moles, particularly from 0.5to 3 moles, per mole of propane. This reaction may usually be conductedunder atmospheric pressure, but may be conducted under a slightlyincreased pressure or a slightly reduced pressure. With respect to otheralkanes such as isobutane, or to mixtures of alkanes and alkenes such aspropane and propene, the composition of the feed gas may be selected inaccordance with the conditions for propane.

[0118] The process of the third aspect of the present invention may beconducted at a temperature of, for example, from 250° C. to 480° C. Morepreferably, the temperature is from 300° C. to 400° C. The gas spacevelocity, SV, in the gas phase reaction is usually within the range offrom 100 to 10,000 hr⁻¹, preferably from 300 to 6,000 hr, morepreferably from 300 to 2,000 hr⁻¹. As a diluent gas, for adjusting thespace velocity and the oxygen partial pressure, an inert gas such asnitrogen, argon or helium can be employed. When ammoxidation of propaneis conducted by the method of the present invention, in addition toacrylonitrile, carbon monoxide, carbon dioxide, acetonitrile,hydrocyanic acid and acrolein may form as by-products.

COMPARATIVE EXAMPLE 1 AND EXAMPLES 1-6 Comparative Example 1

[0119] 12 mL of an aqueous solution containing ammonium heptamolybdatetetrahydrate (1.0M Mo), ammonium metavanadate (0.3M V) and telluric acid(0.23 Te), formed by dissolving the corresponding salts in water at 70°C., was added to a 50 mL pyrex tube. Then 6mL of an aqueous solution ofniobium oxalate (0.25M Nb) and oxalic acid (0.31M) were added thereto.After removing the water at 50° C., under 100 to 40 mmHg, the solidmaterials were further dried in a vacuum oven at 25° C. overnight andthen calcined. (Calcination was effected by placing the solid materialsin an air atmosphere and then heating them to 275° C. at 10° C./min andholding them under the air atmosphere at 275° C. for one hour; theatmosphere was then changed to argon and the material was heated from275° C. to 600° C. at 2° C./min and the material was held under theargon atmosphere at 600° C. for two hours.) The final catalyst (2.5 g)had a nominal composition of Mo₁V_(0.3)Te _(0.23)Nb_(0.125)O_(x). Thecatalyst, thus obtained, was pressed in a mold and then broken andsieved to 10-20 mesh granules for reactor evaluation.

Example 1

[0120] 12 mL of an aqueous solution containing ammonium heptamolybdatetetrahydrate (1.0M Mo), ammonium metavanadate (0.3M V) and telluric acid(0.23 Te), formed by dissolving the corresponding salts in water at 70°C., was added to a 50 mL pyrex tube. Then 6 mL of an aqueous solution ofniobium oxalate (0.25M Nb) and oxalic acid (0.31M) and 1.15 mL ofiridium in 5% HNO₃ (10,000 μg/mL) were added thereto. After removing thewater at 50° C., under 100 to 40 mmHg, the solid materials were fuirtherdried in a vacuum oven at 25° C. overnight and then calcined.(Calcination was effected by placing the solid materials in an airatmosphere and then heating them to 275° C. at 10° C./min and holdingthem under the air atmosphere at 275° C. for one hour; the atmospherewas then changed to argon and the material was heated from 275° C. to600° C. at 2° C./min and the material was held under the argonatmosphere at 600° C. for two hours.) The final catalyst (2.5 g) had anominal composition of Ir_(0.005)Mo₁V_(0.3)Te_(0.23)Nb_(0.125)O_(x). Thecatalyst, thus obtained, was pressed in a mold and then broken andsieved to 10-20 mesh granules for reactor evaluation.

Example 2

[0121] 12 mL of an aqueous solution containing ammonium heptamolybdatetetrahydrate (1.0M Mo), ammonium metavanadate (0.3M V) and telluric acid(0.23 Te), formed by dissolving the corresponding salts in water at 70°C., was added to a 50 mL pyrex tube. Then 6 mL of an aqueous solution ofniobium oxalate (0.25M Nb) and oxalic acid (0.31M) and 2.3 mL of iridiumin 5% HNO₃ (10,000 μg/mL) were added thereto. After removing the waterat 50° C., under 100 to 40 mmHg, the solid materials were further driedin a vacuum oven at 25° C. overnight and then calcined. (Calcination waseffected by placing the solid materials in an air atmosphere and thenheating them to 275° C. at 10° C./min and holding them under the airatmosphere at 275° C. for one hour; the atmosphere was then changed toargon and the material was heated from 275° C. to 600° C. at 2° C./minand the material was held under the argon atmosphere at 600° C. for twohours.) The final catalyst (2.5 g) had a nominal composition of Ir₀₀₁Mo₁V₀ ₃Te_(0.23) Nb_(0.125)O_(x). The catalyst, thus obtained, waspressed in a mold and then broken and sieved to 10-20 mesh granules forreactor evaluation.

Example 3

[0122] 12 mL of an aqueous solution containing ammonium heptamolybdatetetrahydrate (1.0M Mo), ammonium metavanadate (0.3M V) and telluric acid(0.23 Te), formed by dissolving the corresponding salts in water at 70°C., was added to a 50 mL pyrex tube. Then 6 mL of an aqueous solution ofniobium oxalate (0.25M Nb) and oxalic acid (0.31M) and 4.6 mL of iridiumin 5% HNO₃ (10,000 μg/mL) were added thereto. After removing the waterat 50° C., under 100 to 40 mmHg, the solid materials were further driedin a vacuum oven at 25° C. overnight and then calcined. (Calcination waseffected by placing the solid materials in an air atmosphere and thenheating them to 275° C. at 10° C./min and holding them under the airatmosphere at 275° C. for one hour; the atmosphere was then changed toargon and the material was heated from 275° C. to 600° C. at 2° C./minand the material was held under the argon atmosphere at 600° C. for twohours.) The final catalyst (2.5g) had a nominal composition ofIr_(0.02)Mo₁V₀ ₃Te_(0.23)Nb_(0.125)O_(x). The catalyst, thus obtained,was pressed in a mold and then broken and sieved to 10-20 mesh granulesfor reactor evaluation.

Example 4

[0123] 12 mL of an aqueous solution containing ammonium heptamolybdatetetrahydrate (1.0M Mo), ammonium metavanadate (0.3M V) and telluric acid(0.23 Te), formed by dissolving the corresponding salts in water at 70°C., was added to a 50 mL pyrex tube. Then 6mL of an aqueous solution ofniobium oxalate (0.25M Nb) and oxalic acid 00(0.31M) and 0.9 mL of asolution of samarium in 5% HNO₃ (10,000 μg/mL) were added thereto. Afterremoving the water at 50° C., under 100 to 40 mmHg, the solid materialswere further dried in a vacuum oven at 25° C. overnight and thencalcined. (Calcination was effected by placing the solid materials in anair atmosphere and then heating them to 275° C. at 10° C./min andholding them under the air atmosphere at 275° C. for one hour; theatmosphere was then changed to argon and the material was heated from275° C. to 600° C. at 2° C./min and the material was held under theargon atmosphere at 600° C. for two hours.) The final catalyst (2.5 g)had a nominal composition of Sm₀ ₀₀₅Mo₁V_(0.3)Te₀ ₂₃Nb₀ ₁₂₅O_(f). Thecatalyst, thus obtained, was pressed in a mold and then broken andsieved to 10-20 mesh granules for reactor evaluation.

Example 5

[0124] 12 mL of an aqueous solution containing ammonium heptamolybdatetetrahydrate (1.0M Mo), ammonium metavanadate (0.3M V) and telluric acid(0.23 Te), formed by dissolving the corresponding salts in water at 70°C., was added to a 50 mL pyrex tube. Then 6 mL of an aqueous solution ofniobium oxalate (0.25M Nb) and oxalic acid (0.31 M) and 1.8 mL of asolution of samarium in 5% HNO₃ (10,000 μg/mL) were added thereto. Afterremoving the water at 50° C., under 100 to 40 mmHg, the solid materialswere further dried in a vacuum oven at 25° C. overnight and thencalcined. (Calcination was effected by placing the solid materials in anair atmosphere and then heating them to 275° C. at 10° C./min andholding them under the air atmosphere at 275° C. for one hour; theatmosphere was then changed to argon and the material was heated from275° C. to 600° C. at 2° C./min and the material was held under theargon atmosphere at 600° C. for two hours.) The final catalyst (2.5 g)had a nominal composition of Sm₀ ₀₁Mo₁V_(0.3)Te_(0.23) Nb₀ ₁₂₅O_(f). Thecatalyst, thus obtained, was pressed in a mold and then broken andsieved to 10-20 mesh granules for reactor evaluation.

Example 6

[0125] 12 mL of an aqueous solution containing ammonium heptamolybdatetetrahydrate (1.0M Mo), ammonium metavanadate (0.3M V) and telluric acid(0.23 Te), formed by dissolving the corresponding salts in water at 70°C., was added to a 50 mL pyrex tube. Then 6 mL of an aqueous solution ofniobium oxalate (0.25M Nb) and oxalic acid (0.31M) and 3.6 mL of asolution of samarium in 5% HNO₃ (10,000 μg/mL) were added thereto. Afterremoving the water at 50° C., under 100 to 40 mmHg, the solid materialswere further dried in a vacuum oven at 25° C. overnight and thencalcined. (Calcination was effected by placing the solid materials in anair atmosphere and then heating them to 275° C. at 10° C./min andholding them under the air atmosphere at 275° C. for one hour; theatmosphere was then changed to argon and the material was heated from275° C. to 600° C. at 2° C./min and the material was held under theargon atmosphere at 600° C. for two hours.) The final catalyst (2.5g)had a nominal composition of Sm_(0.02)Mo₁V₀ ₃Te₀ ₂₃Nb_(0.125)O_(x). Thecatalyst, thus obtained, was pressed in a mold and then broken andsieved to 10-20 mesh granules for reactor evaluation.

Evaluation and Results

[0126] Catalyst were evaluated in a 10 cm long Pyrex® tube reactor(internal diameter: 3.9 mm). The catalyst bed (4 cm long) was positionedwith glass wool at approximately mid-length in the reactor and washeated with an electric furnace. Mass flow controllers and metersregulated the gas flow rate. The oxidation was conducted using a feedgas stream of propane, steam and air, with a feed ratio ofpropane:steam:air of 1:3:96. The reactor effluent was analyzed by anFTIR. The results (along with reaction temperature and residence time)are shown in Table 1. TABLE 1 Residence Propane Acrylic Acid TemperatureTime Conversion Yield Catalyst (° C.) (sec) (%) (%) Comp. Ex. 1 390 3 4117 Ex. 1 390 3 42 18 Ex. 2 390 3 32 23 Ex. 3 390 3 35 24 Ex. 4 390 3 4127 Ex. 5 390 3 38 27 Ex. 6 390 3 48 32

Comparative Example 2 and Example 7 Comparative Example 2

[0127] In a flask containing 215 g of water, 25.68 g of ammoniumheptamolybdate tetrahydrate (Aldrich Chemical Company), 5.06 g ofammonium metavanadate (Alfa-Aesar) and 7.68 g of telluric acid (AldrichChemical Company) were dissolved upon heating to 70° C. After cooling to40° C., 2.84 g of oxalic acid (Aldrich Chemical Company) was dissolvedin 122.94 g of an aqueous solution of niobium oxalate (H. C. Starck),containing 1.25% Nb. This was then added to the 3 component mixture toobtain a solution. The water of this solution was removed via a rotaryevaporator with a warm water bath at 50° C. and 28 mm/Hg to obtain 46 gof precursor solid. This catalyst precursor solid was calcined in aquartz tube heated to 275° C. at 10° C./min. with a 100 cc/min. flow ofair through the tube and held for one hour, then using a 100 cc/min flowof argon, ramped to 600° C. at 2° C./min and held for 2 hours. Thecatalyst thus obtained was pressed in a mold and then broken and sievedto 10-20 mesh granules for reactor evaluation.

Example 7

[0128] 100 mL of an aqueous solution containing ammonium heptamolybdatetetrahydrate (1.0M Mo), ammonium metavanadate (0.3M V) and telluric acid(0.23 Te), formed by dissolving the corresponding salts in water at 70°C., was added to a 1000 mL rotavap flask. Then 50 mL of an aqueoussolution of niobium oxalate (0.25M Nb) and oxalic acid (0.3 1M) and 30mL of samarium in 5% HNO₃ (10000 μg/mL) were added thereto. Afterremoving the water via a rotary evaporator with a warm water bath at 50°C. and 28 mm/Hg, the solid materials were further dried in a vacuum ovenat 25° C. overnight. This solid precursor were calcined by placing thesolid materials in an air atmosphere and then heating them to 275° C. at10° C./min and holding them under the air atmosphere at 275° C. for onehour; the atmosphere was then changed to argon and the material washeated from 275° C. to 600° C. at 2° C./min and the material was heldunder the argon atmosphere at 600° C. for two hours.

[0129] This calcined materials were then impregnated with 40 mL ofiridium in 10% aqHCl solution followed by drying via rotavap at 50° C.and further drying in a vacuum oven at 25° C. overnight. This driedmaterials were then calcined with the same procedure described above.The final catalyst had a nominal composition of Mo₁ ₀V₀ ₃Te₀₂₃Nb_(0.125)Ir_(0.002)Sm_(0.02)O_(g). The catalyst thus obtained waspressed in a mold and then broken and sieved to 10-20 mesh granules forreactor evaluation.

Evaluation and Results

[0130] Catalysts were evaluated in a 10 cm long Pyrex® tube reactor(internal diameter: 3.9 mm). The catalyst bed (4 cm long) was positionedwith glass wool at approximately mid-length in the reactor and washeated with an electric furnace. Mass flow controllers and metersregulated the gas flow rate. The oxidation was conducted using a feedgas stream of propane, steam and air, with a feed ratio ofpropane:steam:air of 1:3:96. The reactor effluent was analyzed by anFTIR. The results at 390C and 3 second residence time are shown in Table2. TABLE 2 % C3 % AA % CO % CO2 Example Conv. Yield % AA Sel. YieldYield CO/CO2 1 76 10 13 36 27 1.33 2 42 33 79  6  8 0.75

What is claimed is:
 1. A catalyst comprising a promoted mixed metaloxide having the empirical formula A_(a)M_(b)N_(c)X_(d)Ir_(e)Sm_(f)O_(g)wherein A is at least one element selected from the group consisting ofMo and W, M is at least one element selected from the group consistingof V and Ce, N is at least one element selected from the groupconsisting of Te, Sb and Se, and X is at least one element selected fromthe group consisting of Nb, Ta, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni,Pt, Sb, Bi, B, In, As, Ge, Sn, Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr,Ba, Ra, Hf, Pb, P, Pm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu; and wherein,when a=1, b=0.01 to 1.0, c=0.01 to 1.0, d=0.01 to 1.0, e=0 or 0.001 to0.1, f=0 or 0.001 to 0.1 and g is dependent on the oxidation state ofthe other elements, with the proviso that e and f cannot simultaneouslybe
 0. 2. The catalyst according to claim 1, wherein M is V, N is Teand/or Sb and X is is Nb.
 3. The catalyst according to claim 1, whereine=0.
 4. The catalyst according to claim 1, wherein f=0.
 5. The catalystaccording to claim 4, wherein A is Mo and N is Te.
 6. A process forproducing an unsaturated carboxylic acid, which comprises subjecting analkane or a mixture of an alkane and an alkene to a vapor phasecatalytic oxidation reaction in the presence of a catalyst containing apromoted mixed metal oxide having the empirical formulaA_(a)M_(b)N_(c)X_(d)Ir_(e)Sm_(f)O_(g) wherein A is at least one elementselected from the group consisting of Mo and W, M is at least oneelement selected from the group consisting of V and Ce, N is at leastone element selected from the group consisting of Te, Sb and Se, and Xis at least one element selected from the group consisting of Nb, Ta,Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pt, Sb, Bi, B, In, As, Ge, Sn,Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb, P, Pm, Eu, Gd,Dy, Ho, Er, Tm, Yb and Lu; and wherein, when a=1, b=0.01 to 1.0, c=0.01to 1.0, d=0.01 to 1.0, e=0 or0.001 to 0.1, f=0 or 0.001 to 0.1 and g isdependent on the oxidation state of the other elements, with the provisothat e and f cannot simultaneously be
 0. 7. A process for producing anunsaturated nitrile, which comprises subjecting an alkane, or a mixtureof an alkane and an alkene, and ammonia to a vapor phase catalyticoxidation reaction in the presence of a catalyst containing a promotedmixed metal oxide having the empirical formulaA_(a)M_(b)N_(c)X_(d)Ir_(e)Sm_(f)O_(g) wherein A is at least one elementselected from the group consisting of Mo and W, M is at least oneelement selected from the group consisting of V and Ce, N is at leastone element selected from the group consisting of Te, Sb and Se, and Xis at least one element selected from the group consisting of Nb, Ta,Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pt, Sb, Bi, B, In, As, Ge, Sn,Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb, P, Pm, Eu, Gd,Dy, Ho, Er, Tm, Yb and Lu; and wherein, when a=1, b=0.01 to 1.0, c=0.01to 1.0, d=0.01 to 1.0, e=0 or 0.0001 to 0.1, f=0 or 0.001 to 0.1 and gis dependent on the oxidation state of the other elements, with theproviso that e and f cannot simultaneously be
 0. 8. A catalyst producedby the process comprising: (1) admixing compounds of the elements A, M,N, X, Ir and Sm and at least one solvent to form an admixture, wherein Ais at least one element selected from the group consisting of Mo and W,M is at least one element selected from the group consisting of V andCe, N is at least one element selected from the group consisting of Te,Sb and Se, and X is at lest one element selected from the groupconsisting of Nb, Ta, Ti, Al, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ni, Pt, Bi, B,In, As, Ge, Sn, Li, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Hf, Pb,P, Pm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu, and wherein the elements A, M,N, X, Ir and Sm are present in such amounts that the atomic ratio ofA:M:N:X:Ir:Sm is a:b:c:d:e:f and wherein when a=1, b=0.01 to 1.0, c=0.01to 1.0, d=0.01 to 1.0, e=0 or 0.001 to 0.1 and f=0 or 0.001 to 0.1, withthe proviso that e and f cannot simultaneously be 0; (2) removing saidat least one solvent from the admixture to obtain a catalyst precursor;and (3) calcining said catalyst precursor.
 9. A process for producing anunsaturated carboxylic acid, which comprises subjecting an alkane or amixture of an alkane and an alkene to a vapor phase catalytic oxidationreaction in the presence of the catalyst according to claim
 8. 10. Aprocess for producing an unsaturated nitrile, which comprises subjectingan alkane, or a mixture of an alkane and an alkene, and ammonia to avapor phase catalytic oxidation reaction in the presence of the catalystaccording to claim 8.